package com.company;

public class LinkedListQueue<E> implements Queue<E> {
    private class Node {
        public E e;
        public Node next;

        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e) {
            this(e, null);
        }

        public Node() {
            this(null, null);
        }

        @Override
        public String toString() {
            return e.toString();
        }
    }

    private Node head, tail;
    private int size;

    public LinkedListQueue() {
        head = null;
        tail = null;
        size = 0;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    @Override
    public void enqueue(E o) {
        if (tail == null) {
            tail = new Node(o);
            head = tail;
        } else {
            tail.next = new Node(o);
            tail = tail.next;
        }
        size++;

    }

    @Override
    public E dequeue() {
        if (isEmpty())
            throw new IllegalArgumentException("Cannot dequeue from on empty queue.");
        Node retNode = head;
        head = head.next;
        retNode.next = null;
        if (head == null)
            tail = null;
        size--;
        return retNode.e;
    }

    // 1 2 3 4 5
    // 56
    // tail = nul
    // head = nul
    // head= tail
    // tail.next = new nODE()
    // taile = tail.next
    //head
    // head = head.next
    // node retNode = head
    //head.next =
    @Override
    public E getFront() {
        if (isEmpty())
            throw new IllegalArgumentException("queue is empty");
        return head.e;
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        res.append("Queue: front ");
        Node cur = head;
        while (cur != null) {
            res.append(cur + "->");
            cur = cur.next;
        }
        res.append("NULL tail");
        return res.toString();
    }

    public static void main(String[] args) {
        LinkedListQueue<Integer> linkedListStack = new LinkedListQueue<>();
        for (int i=0;i<10;i++){
            linkedListStack.enqueue(i);
            System.out.println(linkedListStack);
            if (i%3==2){
                linkedListStack.dequeue();
                System.out.println(linkedListStack);
            }
        }
    }
    //ArrayStack
    //LinkedListStack
    //ArrayQueue
    //DubleQueue
    //LinkedListQueue
    //n2
    //0n
    //
}
